Insulating material.



UNITED STATES PATENT ()FFIOE.

LAWRENCE E. BARRINGER, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATiON OF NEW YORK.

INSULATING MATERIAL sitions and their production and involves' particularly flexible insulations for electrical coils as in dynamo electric machines, transformers, and so forth.

My novel insulating material comprises a composition made by a novel process of a condensation product of a phenol and an aldehyde, such as formic aldehyde, and pitch derived from the distillation of fatty substances, for example, the viscid residue remaining in the form of an imperfectly formed soap from the distillation of crude oil with an alkali.

Two prominent advantages of my improved insulation are: first, its property of maintaining itsresistivity, and in some cases even increasing in resistance, with a rise of temperature; second, its continued fiexi bility.

Both the condensation products and the above described pitches are wellknown and may be bought in the 0 en market. The pitches are commercially esignated by various names, for instance, stearin (or cotton oil) pitch, wool oil pitch, palm pitch, the two first-named representing residues containing mainly stearic, the third of palmitic acid. These two materials are indistinguishably mixed in accordance with my invention by being dissolved in a common solvent such as amyl acetate. This solution forms a varnish which can be'applied to the electrical coils or can be used for impregnating cambric or other fibrous materialsin order to improve their insulating property or in any other well understood manner. I

The particular proportions of the condensation product and the pitch, of course, will vary somewhat in accordance with the prop- Specification of Letters Patent. Application filed November 21, 1910. Serial No. 593,387.

Patented Mar. 31, 1914.

erty desired in the final 'roduct, but the following examplev will in icate in general the proportions desirable fora coated sheet insulation. About parts by weight of the dry solid initial condensation product are mixed with approximately 30 parts stearin pitch and dissolved in 200 parts of amyl acetate by grinding these materials together, or otherwise agitating them in contact with the solvent. Stearin pitch is the residue remaining from the purification of crude cotton seed oil by caustic soda and as indicated above this substance is chemically in the nature of an imperfectly formed soap. A sheet of cambric coated with this varnish was found to have its insulating resistance increased with a rise of temperature up to 75 C. The insulation as described above retains its flexibility while cambric varnished with linseed oil and similar forms of insulation become brittle after a certain length of time.

What I clainnas new and desire to secure .by Letters Patent of the United States, is,

1. An insulating material containing a phenolic condensation product and a pitch remaining from the distillation of a fatty substance while in contact with alkali.

2. Aninsulating material containing a phenolic condensation product and stearin pitch.

3. An insulating material containing a phenolic condensation product and stearin pitch dissolved in amyl acetate.

4. An insulating material containing a phenolic condensation product and the pitchy residue remaining from the purification of crude cotton seed oil by caustic soda.

5. An insulating material comprising a not and a pitch remaining from the distillation of fatty substances while in contact with an alkali.

6. An insulating material containing a phenolic condensation product and a pitch remaining from the distillation of fatty substances while in contact with an alkali and sheet of fibrous material impregnated with, a. mlxture of a phenolic (.OHdQIlSfitlOll'PlOdenhibiting a, positive temperature resistance In witness. whereof I have hereunto set m ooezificient b1 j hand this 18th day of November,; 1910.

A .flexi e insulating material comf I prising a sheet of fibrous material impreg- LAWRENCE BARRINGER' 5 nated with a, composition containing a. phe- Witnesses:

nolic condensation product and steal-in pitch 5 BENJAMIN B. H dissolvedin a common solvent. I HELEN OBFORD. 

